1. Field of the Invention
The present invention relates to an organic electroluminescent device and a method of preparing the same, and more particularly, to an organic electroluminescent device including a transparent moisture absorption layer formed using an attaching method and a method of preparing the electroluminescent device.
2. Description of the Related Art
A sealed structure is required to prevent deterioration of organic electroluminescent devices by permeation of moisture.
Conventionally, a metallic can or glass is processed in the form of a cap so as to have a groove, and a powder desiccant for absorbing moisture is placed in the groove.
However, the method of placing the desiccant includes complicated processes, and thus is very expensive. Also, the total thickness of substrates increases and a substrate used for sealing cannot be used for front light emission since it is not transparent. Additionally, although the metallic can is structurally firm, an etched glass is structurally weak. Thus, the etched glass can be easily impaired by an external impact.
Japanese Patent Laid-Open Publication No. Hei 9-148066 discloses an organic electroluminescent display device including a laminated body in which an organic luminescent material layer of an organic compound is placed between a pair of electrodes facing each other, an airtight container for shutting off the laminated body from the outside air, and a drying means, such as an alkali metal oxide or an alkali earth metal oxide, placed in the airtight container. This organic electroluminescent display device is thick due to the shape of the airtight container. Also, although the drying means maintains a solid state after adsorbing moisture, it cannot be applied to front light emission since it is opaque. Also, as stated above, since the method of placing the desiccant includes complicated processes, the manufacturing cost of the organic electroluminescent device is high.
To prepare a front light emission type organic electroluminescent device, it is very important to develop processing techniques for manufacturing a transparent sealing layer having moisture absorption property. Transparent sealing layers having moisture absorption property developed up to now are generally prepared by filling a liquid phase type transparent moisture absorption material in a glass cap and heat treating it to form a coating layer.
However, the side portions of the sealing layer may be contaminated during the process of applying the transparent moisture absorption material, and outgasing (e.g., outgasing of a solvent) may be caused during the process of heat treating the applied transparent moisture absorption material, thereby weakening a bonding force between a sealant and a sealing substrate. Thus, a firm sealed structure is not achieved, thereby fatally affecting a life span of the device.